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Madariaga virus (MADV) has recently been associated with severe human disease in Panama, where the closely related Venezuelan equine encephalitis virus (VEEV) also circulates. In June 2017, a fatal MADV infection was confirmed in a community of Darien Province. We conducted a cross-sectional outbreak investigation with human and mosquito collections in July 2017, where sera were tested for alphavirus antibodies and viral RNA. In addition, by applying a catalytic, force-of-infection (FOI) statistical model to two serosurveys from Darien Province in 2012 and 2017, we investigated whether endemic or epidemic alphavirus transmission occurred historically. In 2017, MADV and VEEV IgM seroprevalences were 1.6% and 4.4%, respectively; IgG antibody prevalences were MADV: 13.2%, VEEV: 16.8%, Una virus (UNAV): 16.0%, and Mayaro virus: 1.1%. Active viral circulation was not detected. Evidence of MADV and UNAV infection was found near households, raising questions about its vectors and enzootic transmission cycles. Insomnia was associated with MADV and VEEV infections, depression symptoms were associated with MADV, and dizziness with VEEV and UNAV. Force-of-infection analyses suggest endemic alphavirus transmission historically, with recent increased human exposure to MADV and VEEV in Aruza and Mercadeo, respectively. The lack of additional neurological cases suggests that severe MADV and VEEV infections occur only rarely. Our results indicate that over the past five decades, alphavirus infections have occurred at low levels in eastern Panama, but that MADV and VEEV infections have recently increased-potentially during the past decade. Endemic infections and outbreaks of MADV and VEEV appear to differ spatially in some locations of eastern Panama.

Alphaviruses (Togaviridae, Alphavirus ) are arthropod-borne single-stranded RNA pathogens that cause febrile and neurologic disease in much of Latin America. However, many features of Alphavirus epidemiology remain unknown. In 2011, we undertook a cross-sectional study in Nueva Esperanza, an indigenous community in the Peruvian Amazon. Here, we present the first serologic evidence of Mayaro (MAYV), Venezuelan equine encephalitis (VEE) complex alphavirus, Una (UNAV), and Madariaga (MADV) viruses reported in humans (24%, 16%, 13%, and 1.5%, respectively) from an Amazonian indigenous community in Peru. Hunting activity and cohabiting with hunters were the main risk factors for Mayaro seroconversion, but only hunting was associated with UNAV seropositivity. Our results suggest that alphavirus infection in this region is common, but we highlight the high UNAV seroprevalence found and corroborate the low MADV prevalence reported in this region. Furthermore, MAYV-neutralizing antibodies were also detected in stored samples from wild animals (18%) hunted by Nueva Esperanza inhabitants and another mestizo community located close to Iquitos. Further serological surveys of VEE complex alphaviruses, UNAV, and MADV in wild animals and assessing the ability of the MAYV seropositive species to transmit the virus will be relevant.

Zika virus (ZIKV) was first detected in the Americas in Brazil in 2015, with a rapid spread to surrounding countries. In Panama, the outbreak began in November 2015 in an indigenous community located on the Caribbean side of the country. Zika virus is typically associated with a diffuse rash, fever, and conjunctivitis. It can rarely cause neurologic manifestations, most commonly microcephaly and Guillain-Barré syndrome. Encephalitis and acute encephalomyelitis are known complications, but ZIKV-associated cerebellitis has yet to be reported in the literature. Herein, we report a case of cerebellitis in a patient infected with ZIKV. This patient developed severe frontal headache and vertigo on the third day of illness, and dysarthria and ataxia on the fifth day. After 1 week of hospitalization, the patient completely recovered. The laboratory serological diagnosis was complicated because of the detection of antibodies against dengue, suggesting a secondary flavivirus infection.

Comprehensive comparative phylogenetic analyses were performed on 17 Gamboa serogroup viruses (GAMSVs) from distinct geographic regions in the Americas and other representative members of the genus Orthobunyavirus (Peribunyaviridae), based on small (S), medium (M), and large (L) open reading frame full-length and partial sequences. Genome characterization showed that the GAMSVs divide into four clades or genotypes. The GAMSVs have a genetic organization similar to other orthobunyaviruses, except that they have a larger NSm protein than other orthobunyaviruses. A serosurvey for Gamboa virus antibodies was performed in plasma from birds, other wild animals, and humans living around the Tucuruí hydroelectric dam in Pará state, northern Brazil, a known focus of GAMSV activity. Newborn chicks ( Gallus gallus domesticus ) were experimentally infected with a GAMSV, and the pathogenesis is described. Histopathological changes were primarily in the lungs and liver. Also, a review of the ecology of the GAMSVs in the Americas is included. In sum, this study presents the genomic and evolutionary characterization of the Gamboa group and the potential model of pathogenesis, which would be helpful for diagnostic purposes, epidemiology, and immunopathogenesis studies.

Viruses in the genus Flavivirus (family Flaviviridae) include many arthropod-borne viruses of public health and veterinary importance. However, during the past two decades an explosion of novel insect-specific flaviviruses (ISFs), some closely related to vertebrate pathogens, have been discovered. Although many flavivirus pathogens of vertebrates have been isolated from naturally infected mosquitoes in Panama, ISFs have not previously been reported from the country. This report describes the isolation and characterization of a novel ISF, tentatively named Mercadeo virus (MECDV), obtained from Culex spp. mosquitoes collected in Panama. Two MECDV isolates were sequenced and cluster phylogenetically with cell-fusing agent virus (CFAV) and Nakiwogo virus (NAKV) to form a distinct lineage within the insect-specific group of flaviviruses., (© The American Society of Tropical Medicine and Hygiene.)

We present the first report of a pediatric case of acute disseminated encephalomyelitis (ADEM) associated with Madariaga virus infection (MADV, Alphavirus, Togaviridae; formerly known as South American variants of eastern equine encephalitis virus [EEEV]) in a patient of the 2010 alphaviral epidemic reported in Panama. The patient was admitted to the Hospital del Niño in Panama City with suspected meningitis, exhibited with decreased alertness and disorientation in space and time, hemiparesis, and left Babinski sign. The patient was transferred to the intensive care unit and treated with aciclovir and methylprednisolone. The magnetic resonance imaging (MRI) of the brain revealed multiple hyperintense lesions at T2-weighted images (T2) and fluid-attenuated inversion recovery (FLAIR) on the cortical-subcortical level. Sera samples obtained on days 6 and 12 were immunoglobulin M (IgM) positive for MADV. The findings on the clinical and cerebrospinal analyses, rapid symptom progression as well as neuroimaging, and serologic studies support our diagnosis. Our results suggest that MADV should be included in the etiologic differential diagnosis of ADEM in endemic countries., (© The American Society of Tropical Medicine and Hygiene.)

Chikungunya virus (CHIKV) is a mosquito-borne pathogen that was only endemic in Africa and south Asia until 2005 and 2006, when the virus spread into the Indian Ocean islands, Europe, and Asia. Autochthonous CHIKV transmission in the Caribbean islands was reported in December of 2013. In Panama, two febrile cases were detected in May of 2014: one traveling from Haiti, and the other traveling from the Dominican Republic. After other imported cases were detected, the first autochthonous case was reported in August of the same year. We detected CHIKV viral RNA and isolated the virus from serum samples. The phylogenetic analysis of the two imported isolates and one autochthonous CHIKV isolate indicated that the viruses belong to the Asian lineage in the Caribbean clade and are related to viruses recently identified in Saint Martin island, British Virgin Islands, China, and the Philippines. Although the circulating CHIKV lineages in the Americas have not yet been described, our results suggest that the Asian lineage is circulating in most American countries reporting autochthonous infection., (© The American Society of Tropical Medicine and Hygiene.)

The epidemiology of Chagas disease was studied in five rural communities located in the eastern region of the Panama Province. Serological tests for Trypanosoma cruzi infection revealed a prevalence of 5.88% (12/204). Hemocultures coupled with polymerase chain reaction (PCR) analysis showed a Trypanosoma rangeli infection rate of 5.88% (12/204). An overall trypanosome infection index of 11.76% (24/204) was detected in this population. A total of 121 triatomine specimens were collected in domestic and peridomestic habitats. Rhodnius pallescens was confirmed as the predominant species. Molecular analysis showed that 17.8% (13/73) of the examined insects were positive for T. cruzi, 17.8% (13/73) for T. rangeli, and 35.6% (26/73) presented mixed infections. Among 73 R. pallescens evaluated, 16.4% (12/73) contained opossum blood meals. The epidemiological implications of these findings are discussed.

The first outbreak of hantavirus pulmonary syndrome (HPS) in Central America was documented on the Azuero peninsula of Panama in late 1999 and 2000. Reverse transcriptase-polymerase chain reaction evidence implicated only Choclo virus in symptomatic HPS with a mortality rate of 20%, although two rodent-borne hantaviruses (Choclo virus and Calabazo virus) were identified in the peridomestic habitat. Neighborhood serosurveys around case households found seroprevalence rates as high as 30%, the highest in the Americas except for western Paraguay. We report here population-based serosurveys for 1,346 adults and children in four communities, three on the Azuero peninsula and one in adjacent central Panama. Overall seroprevalence ranged from 33.2% in a population engaged in farming and fishing on Isla de Cañas, to 16.3% and 21.2% in two mainland agricultural communities, to 3.1% in central Panama, with a modest male predominance of 1.2:1. Nine percent of children 4-10 years old were seropositive, and seroprevalence increased with age in all communities, with highest levels of 52% in those 41-50 years old cohort on Isla de Cañas. Univariate analysis identified correlations between seroprevalence and multiple agricultural and animal husbandry activities. However, stepwise logistic regression models identified only raising animals (cows, pigs, goats, poultry) and fishing as significant independent variables. Human infection with hantavirus on the Azuero peninsula, either with Choclo virus or combined with Calabazo virus, is frequent but rarely results in hospitalization due to respiratory illnesses resembling HPS.